1. Technical Field
The present disclosure relates to circuits, and in particular, to a circuit for controlling a rotation speed of a computer fan.
2. Description of Related Art
Generally, a computer fan is used to facilitate removal of heat to keep the temperature of a central processing unit (CPU) within a safe temperature range. The computer fan may be a 3-pin fan which can be adjusted by a voltage signal, or a 4-pin fan which can be adjusted by a pulse width modulation (PWM) signal controlled by a super input/output chip of a motherboard mounting the CPU.
However, in a 3-pin fan motherboard, a 3-pin fan is connected to the motherboard by a 3-pin header mounted on the motherboard, and in a 4-pin fan motherboard, a 4-pin fan is connected to the motherboard by a 4-pin fan header mounted on the motherboard. Though the 3-pin fan can be connected to the 4-pin fan motherboard by the 4-pin header, the 3-pin fan cannot be controlled by the 4-pin fan controller because the 3-pin fan does not have the fourth pin and cannot receive the PWM signal. Therefore, the CPU may be damaged because the heat may not be dissipated properly.